It is known that liquid condensate by-products of gas production (natural gas, associated gases) and crude penetration can contain numerous metallic compounds in trace amounts, generally present in the form of organometallic complexes in which the metal forms bonds with one or more carbon atoms of the organometallic radical.
These metallic compounds are poisons of catalysts used in petroleum transformation processes. In particular, they poison hydrotreating and hydrogenation catalysts by being progessively deposited on the active surface. Metallic compounds are particularly found in heavy cuts from the distillation of tanker crude (nickel, vanadium, arsenic, mercury) or in condensates of natural gas (mercury, arsenic).
Thermal or catalytic cracking treatment of the hydrocarbon cuts metioned hereinabove, for example, their steam cracking for conversion into lighter hydrocarbon cuts, allows elimination of certain metals (for example, nickel, vanadium . . . ). On the other hand, certain other metals (for example, mercury, arsenic . . . ) likely to form volatile compounds and/or being volatile in the elemental state (mercury) are at least partly found in lighter cuts and can thus poison catalysts of subsequent transformation processes. Mercury also presents the risk of provoking corrosion by forming amalgams, for example with aluminum-base alloys, particularly in the parts of the process carried out at temperatures low enough to provoke condensation of liquid mercury (cryogenic fractionation, exchangers).
Processes for elimination of mercury or arsenic in gas phase hydrocarbons are already known and operate in particular in the presence of solid masses which can be called: adsorption, capture, trapping, extraction, or metal transfer masses.
Concerning masses for demercurization, U.S. Pat. No. 3194629 describes masses consisting of sulfur or even iodide deposited on active carbon.
U.S. Pat. No. 4094777 of the applicant describes other masses comprising copper at least partly in the form of a sulfide and a mineral support. These masses can also contain silver.
French application 87-07442 of the applicant describes a specific method for preparation of said masses.
French patent 2534826 describes other masses consisting of elemental sulfur and a mineral support.
Concerning dearsenification:
German patent 2149993 recommends using group VIII metals (nickel, platinum, palladium).
U.S. Pat. No. 4069140 describes using various absorbent masses. Supported iron oxide is described. Use of lead oxide is described in U.S. Pat. No. 3782076 and use of copper oxide in U.S. Pat. No. 3812653.
Thus, although certain products described in earlier works perform well for demercurization or even for dearsenification of gases (hydrogen for example) or gaseous mixtures (natural gas for example), and in particular when the natural gas contains a large quantity of hydrocarbons including three or more carbon atoms, the tests carried out by the applicant show that the same products are revealed to be fairly inefficient once the charges contain compounds other than elemental metals, for example, for arsenic, arsines comprising hydrocarbon chains containing two or more carbon atoms or, for mercury, dimethylmercuride and other mercury compounds comprising hydrocarbon chains including two or more carbon atoms, and possibly other non metallic elements (sulfur, nitrogen . . . ).